Pet Age
Pet Age — runs in your browser. Inputs are not stored.
Dog & cat human age
Enter values, then press Calculate.
A common rule-of-thumb formula. Varies by breed and health; not a veterinary diagnosis.
How to use
- Under type, choose dog or cat. Choosing cat hides the dog-size field.
- For a dog, choose size: small, medium, or large. The default is medium.
- Enter age (years). Decimals such as 0.5 and 3.5 are allowed. The default example is 5 years.
- Press Calculate for an approximate human age (years). It varies by breed and health.
- This is not a veterinary diagnosis. Follow the clinic for vaccines and check-ups.
Key concepts
The pet age calculator converts dog and cat age to a conventional human-age scale. For dogs, after years 1 and 2, size adds per year (small +4, medium +5, large +6). For cats: year 1 → 15, year 2 → 24, then +4 per year. It is not a veterinary diagnosis.
It is not a simple 7× rule such as age 7 = human 49. Not a veterinary diagnosis. Calculation is local. Breed, spay/neuter, and disease change ageing, so error is large. Enter months as a fractional year.
Example
A medium dog at 5 years is shown as 24 through year 2, then 3 × 5 = 39. A large dog at 5 years is higher because the later add is 6. A cat at 5 years is 24 + (3 × 4) = 36. 0.5 years falls in the first-year band, near the size-specific first-year value. A small dog at 8 years adds 6 × 4 = 24 after year 2, around 48. A cat at 10 years is 24 + 32 = 56. A large dog at 3 years adds 1 × 6 after year 2, higher than medium. A cat at 3 years is 24 + 4 = 28.
Related: Body fat calculator · Calorie calculator (BMR·TDEE) · Water intake calculator
Frequently asked questions
Is size needed to calculate cat age?
Cats use a simple year formula. The size field shows only for dogs. Small/large is not needed for cats.
Is pet age sent to a server?
No. Age is not stored.
Is the human-age conversion accurate?
It is a reference approximation and varies by breed, spay/neuter, and disease. It does not replace a check-up.
Can I enter months?
Input is in years. Enter 6 months as 0.5. Three months is 0.25 years.
Is the pet age calculator medical?
No. It is not a veterinary diagnosis. Do not delay clinic care based on this number. It is not for medical use.
Why is a small dog’s human age lower at the same age?
The convention is that large dogs age faster, so the add after year 2 is larger. It is not a scientific constant.
Last reviewed: 2026-09-04